The performance of low bit audio coding systems can be significantly improved for stereo signals when a parametric stereo (PS) coding tool is employed. In such a system, a mono signal is typically quantized and conveyed using a State-of-the-Art audio coder and stereo parameters are estimated and quantized in the encoder and added as side information to the bit stream. In the decoder, the stereo signal is reconstructed from the decoded mono signal with help of stereo parameters.
There are several possible parametric stereo coding variants. Accordingly, there are several encoder types and, in addition to a mono downmix, they generate different stereo parameters that are embedded in the generated bit stream. Tools for such coding have also been standardized. An example of such a standard is MPEG-4 Audio (ISO/IEC 14496-3).
The main idea behind audio coding systems in general and parametric stereo coding in particular, and one of the several challenges of this technical field is to minimize the amount of information that has to be transferred in the bit stream from an encoder to a decoder while still obtaining a good audio quality. A high level of compression of the bit stream information may lead to unacceptable sound quality either because of complex and insufficient calculation processes or because information has been lost in the compression process. A low level of compression of the bit stream information may on the other hand lead to capacity problems which also may result in unacceptable sound quality.
Accordingly, there is a need for improved parametric stereo coding methods.
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